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arXiv 2020年

作者： Yonemaru, N. Kuroyanagi, S. Hobbs, George Takahashi, K. Zhu, X.-J. Coles, W.A. Dai, S. Howard, E. Manchester, R. Reardon, D. Russell, C. Shannon, R. Thyagarajan, N. Spiewak, R. Wang, J.-B. Kumamoto University Graduate School of Science and Technology Kumamoto860-8555 Japan CSIRO Astronomy and Space Science PO Box 76 EppingNSW1710 Australia Nagoya University Graduate School of Science Nagoya464-8601 Japan Instituto de Física Teórica UAM-CSIC Universidad Autonóma de Madrid Cantoblanco Madrid28049 Spain International Research Organization for Advanced Science and Technology Kumamoto University Kumamoto860-8555 Japan School of Physics and Astronomy Monash University VIC3800 Australia OzGrav: Australian Research Council Centre of Excellence for Gravitational Wave Discovery Electrical and Computer Engineering University of California at San Diego San diegoCA United States Department of Physics and Astronomy Macquarie University Sydney2109 Australia Centre for Quantum Dynamics Griffith University BrisbaneQLD4111 Australia Centre for Astrophysics and Supercomputing Swinburne University of Technology P.O. Box 218 HawthornVIC3122 Australia CSIRO Scientific Computing Services Australian Technology Park Locked Bag 9013 AlexandriaNSW1435 Australia National Radio Astronomy Observatory 1003 Lopezville Rd SocorroNM87801 United States Xinjiang Astronomical Observatory Chinese Academy of Science 150 Science 1-Street UrumqiXinjiang830011 China Key Laboratory of Radio Astronomy Chinese Academy of Science 150 Science 1-Street UrumqiXinjiang830011 China

Cosmic strings are potential gravitational wave (GW) sources that can be probed by pulsar timing arrays (PTAs). In this work we develop a detection algorithm for a GW burst from a cusp on a cosmic string, and apply it to Parkes PTA data. We find four events with a false alarm probability less than 1%. However further investigation shows that all of these are likely to be spurious. As there are no convincing detections we place upper limits on the GW amplitude for different event durations. From these bounds we place limits on the cosmic string tension of G μ∼ 10−5, and highlight that this bound is independent from those obtained using other techniques. We discuss the physical implications of our results and the prospect of probing cosmic strings in the era of Square Kilometre Array (SKA). © 2020, CC BY.

关键词： Pulsars

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The parkes pulsar timing array project: Second data release

arXiv

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arXiv 2020年

作者： Kerr, M. Reardon, D.J. Hobbs, G. Shannon, R.M. Manchester, R.N. Dai, S. Russell, C.J. Zhang, S.-B. van Straten, W. Oslowski, S. Parthasarathy, A. Spiewak, R. Bailes, M. Bhat, N.D.R. Cameron, A.D. Coles, W.A. Dempsey, J. Deng, X. Goncharov, B. Kaczmarek, J.F. Keith, M.J. Lasky, P.D. Lower, M.E. Preisig, B. Sarkissian, J.M. Toomey, L. Wang, H. Wang, J. Zhang, L. Zhu, X. Space Science Division Naval Research Laboratory WashingtonDC20375-5352 United States Centre for Astrophysics and Supercomputing Swinburne University of Technology P.O. Box 218 HawthornVIC3122 Australia CSIRO Astronomy and Space Science Australia Telescope National Facility PO Box 76 EppingNSW1710 Australia CSIRO Scientific Computing Australian Technology Park Locked Bag 9013 AlexandriaNSW1435 Australia University of Chinese Academy of Sciences Beijing100049 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing210008 China International Centre for Radio Astronomy Research University of Western Australia CrawleyWA6009 Australia Institute for Radio Astronomy & Space Research Auckland University of Technology Private Bag 92006 Auckland1142 New Zealand International Centre for Radio Astronomy Research Curtin University BentleyWA6102 Australia Department of Electrical and Computer Engineering University of California San DiegoCA92093 United States CSIRO Information Management & Technology GPO Box 1700 CanberraACT2601 Australia School of Physics and Astronomy Monash University VIC3800 Australia CSIRO Astronomy and Space Science Parkes Observatory 473 Telescope road ParkesNSW2870 Australia Jodrell Bank Centre for Astrophysics Department of Physics and Astronomy University of Manchester Alan Turing Building Oxford Road ManchesterM13 9PL United Kingdom School of Physics and Electronic Engineering Guangzhou University Guangzhou510006 China Xinjiang Astronomical Observatory Chinese Academy of Sciences 150 Science 1-Street Urumqi Xinjiang830011 China National Astronomical Observatories Chinese Academy of Sciences A20 Datun Road Chaoyang District Beijing100101 China

We describe 14 years of public data from the Parkes Pulsar Timing Array (PPTA), an ongoing project that is producing precise measurements of pulse times of arrival from 26 millisecond pulsars using the 64-m Parkes radio telescope with a cadence of approximately three weeks in three observing bands. A comprehensive description of the pulsar observing systems employed at the telescope since 2004 is provided, including the calibration methodology and an analysis of the stability of system components. We attempt to provide full accounting of the reduction from the raw measured Stokes parameters to pulse times of arrival to aid third parties in reproducing our results. This conversion is encapsulated in a processing pipeline designed to track provenance. Our data products include pulse times of arrival for each of the pulsars along with an initial set of pulsar parameters and noise models. The calibrated pulse profiles and timing template profiles are also available. These data represent almost 21,000 hrs of recorded data spanning over 14 years. After accounting for processes that induce time-correlated noise, 22 of the pulsars have weighted root-mean-square timing residuals of Copyright © 2020, The Authors. All rights reserved.

关键词： Pulsars

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The properties of the interstellar medium in dusty, star-forming galaxies at z ∼ 2 − 4: The shape of the CO spectral line energy distributions

arXiv

引用

arXiv 2024年

作者： Taylor, Dominic J. Swinbank, A.M. Smail, Ian Puglisi, Annagrazia Birkin, Jack E. Dudzevičiūte, Ugne Chen, Chian-Chou Ikarashi, S. Castillo, Marta Frias Weiß, Axel Li, Zefeng Chapman, Scott C. Jansen, Jasper Jiménez-Andrade, E.F. Morabito, Leah K. Murphy, Eric J. Rybak, Matus van der Werf, P.P. Centre for Extragalactic Astronomy Department of Physics Durham University South Road DurhamDH1 3LE United Kingdom School of Physics and Astronomy University of Southampton HighfieldSO17 1BJ United Kingdom Department of Physics and Astronomy Texas A&M University 4242 TAMU College StationTX77843-4242 United States George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy Texas A&M University 4242 TAMU College StationTX77843-4242 United States Max-Planck-Institut für Astronomie Königstuhl 17 HeidelbergD-69117 Germany No. 1 Sec. 4 Roosevelt Road Taipei10617 Taiwan Department of Physics General Studies College of Engineering Nihon University 1 Nakagawara Tokusada Tamuramachi Koriyama Fukushima963-8642 Japan National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Leiden Observatory Leiden University P.O. Box 9513 Leiden2300 RA Netherlands Max Planck Institut für Radioastronomie Auf dem Hügel 69 BonnD-53121 Germany Department of Physics and Atmospheric Science Dalhousie University Halifax HalifaxNSB3H 3J5 Canada National Radio Astronomy Observatory 520 Edgemont Road CharlottesvilleVA22903 United States Instituto de Radioastronomía y Astrofísica Universidad Nacional Autónomia de México Antigua Carretera a Pátzcuaro # 8701 Ex-Hda. San José de la Huerta Michoacán C.P Morelia58089 Mexico Argelander Institut für Astronomie Universität Bonn Auf dem Hügel 71 BonnD-53121 Germany Institute for Computational Cosmology Department of Physics University of Durham South Road DurhamDH1 3LE United Kingdom Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technology Mekelweg 4 Delft2628 CD Netherlands SRON - Netherlands Institute for Space Research Niels Bohrweg 4 Leiden2333 Netherlands

The molecular gas in the interstellar medium (ISM) of star-forming galaxy populations exhibits diverse physical properties. We investigate the 12CO excitation of twelve dusty, luminous star-forming galaxies at ∼ 2–4 by combining observations of the 12CO from up = 1 to up = 8. The spectral line energy distribution (SLED) has a similar shape to NGC 253, M82, and local ULIRGs, with much stronger excitation than the Milky Way inner disc. By combining with resolved dust continuum sizes from high-resolution 870-µm ALMA observations and dust mass measurements determined from multi-wavelength SED fitting, we measure the relationship between the 12CO SLED and probable physical drivers of excitation: star-formation efficiency, the average intensity of the radiation field and the star-formation rate surface density. The primary driver of high-up12CO excitation in star-forming galaxies is star-formation rate surface density. We use the ratio of the CO(3–2) and CO(6–5) line fluxes to infer the CO excitation in each source and find that the average ratios for our sample are elevated compared to observations of low-redshift, less actively star-forming galaxies and agree well with predictions from numerical models that relate the ISM excitation to the star-formation rate surface density. The significant scatter in the line ratios of a factor ≈ 3 within our sample likely reflects intrinsic variations in the ISM properties which may be caused by other effects on the excitation of the molecular gas, such as cosmic ray ionization rates and mechanical heating through turbulence dissipation. © 2024, CC BY.

关键词： Cosmic rays

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A Comparative Study of the Ground State Transitions of CO and [C I] as Molecular Gas Tracers at High Redshift

arXiv

引用

arXiv 2024年

作者： Castillo, Marta Frias Rybak, Matus Hodge, Jacqueline A. van der Werf, Paul Smail, Ian Butterworth, Joshua Jansen, Jasper Topkaras, Theodoros Chen, Chian-Chou Chapman, Scott C. Weiss, Axel Algera, Hiddo Birkin, Jack E. da Cunha, Elisabete Chen, Jianhang Dannerbauer, Helmut Jiménez-Andrade, E.F. Ikarashi, Soh Liao, Cheng-Lin Murphy, Eric J. Swinbank, A.M. Walter, Fabian Rivera, Gabriela Calistro Ivison, R.J. Del Lagos, Claudia P. Leiden Observatory Leiden University P.O. Box 9513 Leiden2300 RA Netherlands Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technology Mekelweg 4 Delft2628 CD Netherlands SRON - Netherlands Institute for Space Research Niels Bohrweg 4 Leiden2333 CA Netherlands Centre for Extragalactic Astronomy Department of Physics Durham University South Road DurhamDH1 3LE United Kingdom I. Physikalisches Institut Universität zu Köln Zülpicher Str. 77 Köln50937 Germany No.1 Section 4 Roosevelt Road Taipei10617 Taiwan Department of Physics and Atmospheric Science Dalhousie University Halifax HalifaxNSB3H 3J5 Canada Max Planck Institut für Radioastronomie Auf dem Hügel 69 BonnD-53121 Germany Hiroshima Astrophysical Science Center Hiroshima University 1-3-1 Kagamiyama Hiroshima Higashi-Hiroshima739-8526 Japan National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo Japan Department of Physics and Astronomy Texas A&M University 4242 TAMU College StationTX77843-4242 United States George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy Texas A&M University 4242 TAMU College StationTX77843-4242 United States International Centre for Radio Astronomy Research University of Western Australia 35 Stirling Hwy CrawleyWA6009 Australia Australia Karl-Schwarzschild-Straße 2 Garching bei München85748 Germany Tenerife La LagunaE-38205 Spain Dpto. Astrofísica Universidad de la Laguna Tenerife La LagunaE-38206 Spain Instituto de Radioastronomía y Astrofísica Universidad Nacional Autónoma de México Antigua Carretera a Pátzcuaro # 8701 Ex-Hda. San José de la Huerta Michoacán MoreliaC.P. 58089 Mexico Department of Physics General Studies College of Engineering Nihon University 1 Nakagawara Tokusada Tamuramachi Fukushima Koriyama963-8642 Japan National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Graduate Institute of Astrophysics Na

The CO(1-0) and [C I](1-0) emission lines are well-established tracers of cold molecular gas mass in local galaxies. At high redshift, where the interstellar medium (ISM) is likely to be denser, there have been limited direct comparisons of both ground state transitions. Here we present a study of CO(1-0) and [C I](1-0) emission in a sample of 20 unlensed dusty, star-forming galaxies at z = 2 − 5. The CO(1-0)/[C I](1-0) ratio is constant up to at least z = 5, supporting the use of [CI](1-0) as a gas mass tracer. PDR modelling of the available data indicates a median H2 density of log(n [cm−3]) = 4.7 ± 0.2, and UV radiation field log(GUV [G0]) = 3.2 ± 0.2. We use the CO(1-0), [C I](1-0) and 3mm dust continuum measurements to cross-calibrate the respective gas mass conversion factors, finding no dependence of these factors on either redshift or infrared luminosity. Assuming a variable CO conversion factor then implies [C I] and dust conversion factors that differ from canonically assumed values but are consistent with the solar/super-solar metallicities expected for our sources. Radiative transfer modelling shows that the warmer CMB at high redshift can significantly affect the [C I] as well as CO emission, which can change the derived molecular gas masses by up to 70% for the coldest kinetic gas temperatures expected. Nevertheless, we show that the magnitude of the effect on the ratio of the tracers is within the known scatter of the L′CO − L′[CI] relation. Further determining the absolute decrease of individual line intensities will require well-sampled spectral line energy distributions (SLEDs) to model the gas excitation conditions in more detail. Copyright © 2024, The Authors. All rights reserved.

关键词： Ground state

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Multi-Wavelength Analysis of AT 2023sva: a Luminous Orphan Afterglow With Evidence for a Structured Jet

arXiv

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arXiv 2025年

作者： Srinivasaragavan, Gokul P. Perley, Daniel A. Ho, Anna Y.Q. O’Connor, Brendan de Ugarte Postigo, Antonio Sarin, Nikhil Cenko, S. Bradley Sollerman, Jesper Rhodes, Lauren Green, David A. Svinkin, Dmitry S. Bhalerao, Varun Waratkar, Gaurav Nayana, A.J. Chandra, Poonam Miller, M. Coleman Malesani, Daniele B. Ryan, Geoffrey Srijan, Suryansh Bellm, Eric C. Burns, Eric Titterington, David J. Stone, Maria B. Purdum, Josiah Ahumada, Tomás Anupama, G.C. Barway, Sudhanshu Coughlin, Michael W. Drake, Andrew Fender, Rob Agüí Fernández, José F. Frederiks, Dmitry D. Geier, Stefan Graham, Matthew J. Kasliwal, Mansi M. Kulkarni, S.R. Kumar, Harsh Li, Maggie L. Laher, Russ R. Lysenko, Alexandra L. Parwani, Gopal Perley, Richard A. Ridnaia, Anna V. Salgundi, Anirudh Smith, Roger Sravan, Niharika Swain, Vishwajeet Thöne, Christina C. Tsvetkova, Anastasia E. Ulanov, Mikhail V. Vail, Jada Wise, Jacob L. Wold, Avery Department of Astronomy University of Maryland College ParkMD20742 United States Joint Space-Science Institute University of Maryland College ParkMD20742 United States Astrophysics Science Division NASA Goddard Space Flight Center 8800 Greenbelt Rd GreenbeltMD20771 United States Astrophysics Research Institute Liverpool John Moores University 146 Brownlow Hill LiverpoolL3 5RF United Kingdom Department of Astronomy Cornell University IthacaNY14853 United States McWilliams Fellow McWilliams Center for Cosmology and Astrophysics Department of Physics Carnegie Mellon University PittsburghPA15213 United States Université de la Côte d’Azur Observatoire de la Côte d’Azur CNRS Artemis NiceF-06304 France Aix Marseille Univ CNRS LAM Marseille France Oskar Klein Centre for Cosmoparticle Physics Department of Physics Stockholm University AlbaNova StockholmSE-106 91 Sweden Nordita Stockholm University KTH Royal Institute of Technology Hannes Alfvens vag 12 StockholmSE-106 91 Sweden Oskar Klein Centre Department of Astronomy Stockholm University AlbaNova StockholmSE-10691 Sweden Trottier Space Institute at McGill 3550 Rue University MontrealQCH3A 2A7 Canada Department of Physics McGill University 3600 Rue University MontrealQCH3A 2T8 Canada Astrophysics Group Cavendish Laboratory 19 J J Thomson Avenue CambridgeCB3 0HE United Kingdom Ioffe Institute Polytekhnicheskaya 26 St. Petersburg194021 Russia Department of Physics IIT Bombay Powai Mumbai400076 India National Centre for Radio Astrophysics Tata Institute of Fundamental Research Pune University Campus Ganeshkhind Pune411007 India National Radio Astronomy Observatory 520 Edgemont Rd CharlottesvilleVA22903 United States Denmark Niels Bohr Institute University of Copenhagen Jagtvej 128 Copenhagen2200 Denmark Department of Astrophysics IMAPP Radboud University Nijmegen P.O. Box 9010 Nijmegen6500 GL Netherlands Perimeter Institute for Theoretical Physics WaterlooONN2L

We present multi-wavelength analysis of ZTF23abelseb (AT 2023sva), an optically discovered fast-fading (⃤mr = 2.2 mag in ⃤t = 0.74 days), luminous (Mr ∼ −30.0 mag) and red (g − r = 0.50 mag) transient at z = 2.28 with accompanying luminous radio emission. AT 2023sva does not possess a γ-ray burst (GRB) counterpart to an isotropic equivalent energy limit of Eγ,iso 52 erg, determined through searching γ-ray satellite archives between the last non-detection and first detection, making it the sixth example of an optically-discovered afterglow with a redshift measurement and no detected GRB counterpart. We analyze AT 2023sva’s optical, radio, and X-ray observations to characterize the source. From radio analyses, we find the clear presence of strong interstellar scintillation (ISS) 72 days after the initial explosion, allowing us to place constraints on the source’s angular size and bulk Lorentz factor. When comparing the source sizes derived from ISS of orphan events to those of the classical GRB population, we find orphan events have statistically smaller source sizes. We also utilize Bayesian techniques to model the multi-wavelength afterglow. Within this framework, we find evidence that AT 2023sva possesses a shallow power-law structured jet viewed slightly off-axis (θv = 0.07 ± 0.02) just outside of the jet’s core opening angle (θc = 0.06 ± 0.02). We determine this is likely the reason for the lack of a detected GRB counterpart, but also investigate other scenarios. AT 2023sva’s evidence for possessing a structured jet stresses the importance of broadening orphan afterglow search strategies to a diverse range of GRB jet angular energy profiles, to maximize the return of future optical surveys. Copyright © 2025, The Authors. All rights reserved.

关键词： Fading (radio)

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The ALMA REBELS Survey: Discovery of a massive, highly star-forming and morphologically complex ULIRG at z = 7.31

arXiv

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arXiv 2023年

作者： Hygate, A.P.S. Hodge, J.A. da Cunha, E. Rybak, M. Schouws, S. Inami, H. Stefanon, M. Graziani, L. Schneider, R. Dayal, P. Bouwens, R.J. Smit, R. Bowler, R.A.A. Endsley, R. Gonzalez, V. Oesch, P.A. Stark, D.P. Algera, H.S.B. Aravena, M. Barrufet, L. Ferrara, A. Fudamoto, Y. Hilhorst, J.H.A. De Looze, I. Nanayakkara, T. Pallottini, A. Riechers, D.A. Sommovigo, L. Topping, M.W. van der Werf, P. Leiden Observatory Leiden University P.O. Box 9513 Leiden2300 RA Netherlands International Centre for Radio Astronomy Research University of Western Australia 35 Stirling Hwy Crawley26WA 6009 Australia 2601 Australia Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technology Delft Netherlands Hiroshima Astrophysical Science Center Hiroshima University 1-3-1 Kagamiyama Higashi-Hiroshima Hiroshima739-8526 Japan Departament d’Astronomia i Astrofísica Universitat de València C. Dr. Moliner 50 Burjassot ValènciaE-46100 Spain Dipartimento di Fisica Sapienza Università di Roma Piazzale Aldo Moro 5 RomaI-00185 Italy INAF Osservatorio Astrofisico di Arcetri Largo E. Fermi 5 FirenzeI-50125 Italy Sapienza School for Advanced Studies Viale Regina Elena 291 RomaI-00161 Italy INAF/Osservatorio Astronomico di Roma via Frascati 33 Monte Porzio Catone RomaI-00078 Italy Istituto Nazionale di Fisica Nucleare Sezione di Roma1 Piazzale Aldo Moro 2 RomaI-00185 Italy Jodrell Bank Centre for Astrophysics Department of Physics and Astronomy School of Natural Sciences The University of Manchester ManchesterM13 9PL United Kingdom Steward Observatory University of Arizona 933 N Cherry Ave TucsonAZ85721 United States Departmento de Astronomia Universidad de Chile Casilla 36-D Santiago7591245 Chile Camino del Observatorio 1515 Las Condes Santiago7591245 Chile Observatoire de Genève VersoixCH-1290 Switzerland Niels Bohr Institute University of Copenhagen Jagtvej 128 København NDK-2200 Denmark National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo Japan Nucleo de Astronomia Facultad de Ingenieria y Ciencias Universidad Diego Portales Av. Ejercito 441 Santiago Chile Scuola Normale Superiore Piazza dei Cavalieri 7 PisaI- 50126 Italy Waseda Research Institute for Science and Engineering Faculty of Science and Engineering Waseda University 3-4-1 Okubo Shinjuku Tokyo169-8555 Japan Sterrenkun

We present Atacama Large Millimeter/Submillimeter Array (ALMA) [Cii] and ∼ 158μm continuum observations of REBELS-25, a massive, morphologically complex ultra-luminous infrared galaxy (ULIRG;LIR = 1.5+−00.85 × 1012 L) at z = 7.31, spectroscopically confirmed by the Reionization Era Bright Emission Line Survey (REBELS) ALMA Large Programme. REBELS-25 has a significant stellar mass of M∗ = 8+−42 × 109 M . From dust-continuum and ultraviolet observations, we determine a total obscured + unobscured star formation rate of SFR = 199+−10163 M yr−1. This is about four times the SFR estimated from an extrapolated main-sequence. We also infer a [Cii]-based molecular gas mass of MH2 = 5.1+−52.16 × 1010 M, implying a molecular gas depletion time of tdepl,H2 = 0.3+−00.32 Gyr. We observe a [Cii] velocity gradient consistent with disc rotation, but given the current resolution we cannot rule out a more complex velocity structure such as a merger. The spectrum exhibits excess [Cii] emission at large positive velocities (∼ 500 km s−1), which we interpret as either a merging companion or an outflow. In the outflow scenario, we derive a lower limit of the mass outflow rate of 200 M yr−1, which is consistent with expectations for a star formation-driven outflow. Given its large stellar mass, SFR and molecular gas reservoir ∼ 700 Myr after the Big Bang, we explore the future evolution of REBELS-25. Considering a simple, conservative model assuming an exponentially declining star formation history, constant star formation efficiency, and no additional gas inflow, we find that REBELS-25 has the potential to evolve into a galaxy consistent with the properties of high-mass quiescent galaxies recently observed at z ∼ 4. Copyright © 2023, The Authors. All rights reserved.

关键词： Galaxies

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Spirals and clumps in V960 Mon: signs of planet formation via gravitational instability around an FU Ori star?

arXiv

引用

arXiv 2023年

作者： Weber, Philipp Pérez, Sebastián Zurlo, Alice Miley, James Hales, Antonio Cieza, Lucas Principe, David Cárcamo, Miguel Garufi, Antonio Kóspál, Ágnes Takami, Michihiro Kastner, Joel Zhu, Zhaohuan Williams, Jonathan Departamento de Física Universidad de Santiago de Chile Av. Victor Jara Santiago3659 Chile Chile Universidad de Santiago de Chile Chile Núcleo de Astronomía Facultad de Ingeniería y Ciencias Universidad Diego Portales Av. Ejercito 441 Santiago Chile Escuela de Ingeniería Industrial Facultad de Ingeniería y Ciencias Universidad Diego Portales Av. Ejercito 441 Santiago Chile Joint ALMA Observatory Alonso de Córdova 3107 Vitacura Santiago763-0355 Chile Los Abedules 3085 Office 701 Vitacura Santiago Chile National Radio Astronomy Observatory 520 Edgemont Road CharlottesvilleVA22903-2475 United States MIT Kavli Institute for Astrophysics and Space Research 77 Massachusetts Avenue CambridgeMA02139 United States Faculty of Engineering Computer Engineering Department Chile INAF Osservatorio Astrofisico di Arcetri Largo Enrico Fermi 5 Firenze50125 Italy Konkoly-Thege Miklós út 15-17 Budapest1121 Hungary CSFK MTA Centre of Excellence Konkoly Thege Miklós út 15-17 Budapest1121 Hungary ELTE Eötvös Loránd University Institute of Physics Pázmány Péter sétány 1/A Budapest1117 Hungary Max Planck Institute for Astronomy Königstuhl 17 Heidelberg69117 Germany Institute of Astronomy and Astrophysics Academia Sinica 11F of Astronomy-Mathematics Building No.1 Sec. 4 Roosevelt Rd Taipei10617 Taiwan School of Physics & Astronomy Rochester Institute of Technology 1 Lomb Memorial Dr. RochesterNY14623 United States Department of Physics and Astronomy University of Nevada Las Vegas 4505 S. Maryland Pkwy Las VegasNV89154 United States Nevada Center for Astrophysics University of Nevada Las VegasNV89154 United States Institute for Astronomy University of Hawai’i at Manoa HonoluluHI96822 United States

The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of gravitational instability occurring on planetary scales. This study discusses the significance of this finding for planet formation and its potential connection with the outbursting state of V960 Mon. © 2023, CC BY-NC-SA.

关键词： Stars

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Field Tests of Digital Terrestrial Multimedia Broadcasting System RAVIS

Field Tests of Digital Terrestrial Multimedia Broadcasting S...

引用

engineering and Telecommunication (EnT-MIPT)

作者： Alexander V. Dvorkovich Viktor P. Dvorkovich Vladimir A. Irtyuga Kirill S. Mityagin MIPT -School of Radio Engineering and Computer Technology Moscow Institute of Physics and Technology Moscow Russian Federation Multimedia Technology and Telecommunication Dep. Moscow Institute of Physics and Technology Moscow Russian Federation Multimedia Systems and Technology Lab. Moscow Institute of Physics and Technology Moscow Russian Federation

Field tests of digital terrestrial multimedia broadcasting system RAVIS have been held in 2017-2018 in two test zones in Russian Federation - Kazan city (Tatarstan Republic) and Izhevsk city (Udmurtia Republic). Fixed... 详细信息

ISBN: (纸本)9781728104331

关键词： Multimedia communication Receivers radio transmitters Modulation Urban areas Digital multimedia broadcasting

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Nonlinear Quantization Method for Wavelet-Based Video Codec

Nonlinear Quantization Method for Wavelet-Based Video Codec

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engineering and Telecommunication (EnT-MIPT)

作者： Dam Trong Nam Gennady Yu. Gryzov Alexander V. Dvorkovich Viktor P. Dvorkovich Multimedia Systems and Technology Lab. Moscow Institute of Physics and Technology Moscow Russian Federation MIPT-School of Radio Engineering and Computer Technology Moscow Institute of Physics and Technology Moscow Russian Federation Multimedia Technology and Telecommunication Dep. Moscow Institute of Physics and Technology Moscow Russian Federation

ISBN: (纸本)9781728104331

This paper is dedicated to the research and development of quantization methods for wavelet-based video codec. Uniform, nonlinear quantization method and their potential applications for wavelet-based video codec Dirac have been investigated. The optimized quantization method for wavelet-based video codec have been proposed based on analysis of the processing results for various video types using quantization methods mentioned above. The processing results for various types of video show that the proposed method provides up to 4.2% bitrate saving for low distortion level in the intra-frame coding mode, up to 9.8% bitrate reduction for low distortion level and up to 11.2% bitrate saving for medium (acceptable) distortion level in the inter-frame coding mode compared to the uniform quantization method implemented in video codec Dirac.

关键词： Quantization (signal) Video codecs Wavelet transforms Distortion Bit rate Image coding

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Content-preserving image stitching with regular boundary constraints

arXiv

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arXiv 2018年

作者： Zhang, Yun Lai, Yu-Kun Zhang, Fang-Lue Institute of Zhejiang Radio and TV Technology Communication University of Zhejiang Hangzhou310018 China School of Computer Science and Informatics Cardiff University WalesCF24 3AA United Kingdom School of Engineering and Computer Science Victoria University of Wellington New Zealand

This paper proposes an approach to contentpreserving image stitching with regular boundary constraints, which aims to stitch multiple images to generate a panoramic image with regular boundary. Existing methods treat image stitching and rectangling as two separate steps, which may result in suboptimal results as the stitching process is not aware of the further warping needs for rectangling. We address these limitations by formulating image stitching with regular boundaries in a unified optimization. Starting from the initial stitching results produced by traditional warping-based optimization, we obtain the irregular boundary from the warped meshes by polygon Boolean operations which robustly handle arbitrary mesh compositions, and by analyzing the irregular boundary construct a piecewise rectangular boundary. Based on this, we further incorporate straight line preserving and regular boundary constraints into the image stitching framework, and conduct iterative optimization to obtain an optimal piecewise rectangular boundary, thus can make the boundary of stitching results as close as possible to a rectangle, while reducing unwanted distortions. We further extend our method to selfie expansion and video stitching, by integrating the portrait preservation and temporal coherence into the optimization. Experiments show that our method efficiently produces visually pleasing panoramas with regular boundaries and unnoticeable distortions. Copyright © 2018, The Authors. All rights reserved.

关键词： Geometry

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